1. Field of the Invention
The present invention relates to an exhaust-gas muffler.
2. Discussion of the Background
An exhaust-gas muffler configured as follows has been known from Japanese Patent Application Publication No. 2007-321595: in the exhaust-gas muffler, a relief valve is provided between an upstream exhaust-gas chamber and a downstream exhaust-gas chamber among a plurality of exhaust-gas chambers which are formed in a casing and through which exhaust gas flows sequentially, and includes a shutter member placed to face an open end of a gas passage between the upstream exhaust-gas chamber and the downstream exhaust-gas chamber, the open end of the gas passage being open to the downstream exhaust-gas chamber, a spring for biasing the shutter member in such a direction that the gas passage is closed, and a seal member fastened to the shutter member so as to be capable of coming in contact with the whole circumference of the open end of the gas passage to the downstream exhaust-gas chamber. In the exhaust-gas muffler, the seal member is formed into a ring shape corresponding to an open end of a tube member forming the gas passage to the downstream exhaust-gas chamber to reduce hammering sound produced by a closing action of the relief valve.